Concrete reinforcement cable tensioner

ABSTRACT

A concrete reinforcement cable tensioner ( 10 ) has a cable gripper ( 60 ) with its base end ( 87 ) mounted to a flange ( 18 ) which is secured to the tensioning cylinders ( 12, 14 ) by abutting a shoulder on the outside of the cylinders ( 12, 14 ). An auxiliary retraction spring ( 94 ) is contained in a tubular handle ( 86 ) which is fixed to the flange ( 18 ) and the spring ( 94 ) acts on a rod ( 92 ) which extends beyond the handle ( 86 ) and has its distal end fixed to a yoke ( 104 ) which connects the piston rods ( 30 ) of the cylinders ( 12, 14 ) and on which a seat ( 108 ) for bearing against the concrete slab is mounted. The base ends ( 24 ) of the tensioning cylinders ( 12, 14 ) are hydraulically connected by a manifold ( 16 ) which is common to the cylinders ( 12, 14 ) and binds the base ends ( 24 ) of the cylinders ( 12, 14 ) together.

This claims the benefit of U.S. Provisional Patent Application No.60/037,635 filed Jan. 17, 1997.

FIELD OF THE INVENTION

This invention relates to a hydraulic cylinder operated device fortensioning reinforcement cables in green concrete.

DISCUSSION OF THE PRIOR ART

Concrete is sometimes reinforced with braided wire cables, sometimesreferred to as wire rope. For example, a grid of such cables may beplaced in a concrete form, the concrete poured and allowed to set into asemi-cured state, referred to as green concrete, and while green thecables, which extend beyond the concrete slab, are tensioned so thatthey are under a tensile stress, thereby exerting a compressive load onthe slab. The cables extend all the way through the slab and beyond theside edges of it, so that they may be grasped by the tensioningmechanism. Typically, one end of each cable is anchored to the slab atone side edge and the other end is grasped by the hydraulic tensioningdevice.

Such tensioning devices typically have two hydraulic cylinders with agripping mechanism fixed to the cylinders for grasping the cable and aseat secured to the piston rods of the cylinders for bearing (directlyor indirectly) against the side edge of the concrete slab so that atension of a high magnitude can be exerted on the cable. A seat whichmates with the tensioning tool is typically cast into the side edge ofthe concrete where the cable comes out and the cable extends through theseat and through a grommet in the seat which only permits one waymovement of the cable through the grommet. In other words, when thecable is being tensioned the cable can move through the grommet, butwhen the cable attempts to move backwardly through the grommet back intothe slab, the grommet engages the cable and tightens around it toprevent such reverse movement and consequent reduction in the tensileforce on the cable. Tensioning devices for performing this operation,seats and grommets are all well known.

In the currently existing tensioning devices, a significant length ofcable must be extended past the side edge of the slab where thetensioning device is operated to be grasped by the device. If the cablelength extending beyond the side edge of the slab is less than thatrequired by the tensioning device to grip the cable, for example if thecable is cut too short, or if when pouring the concrete a worker stepson the cable, thereby pulling it back through the seat which is castinto the slab, an extension cable may need to be assembled to the end ofthe cable so that it can be grasped by the tensioner. This can be a verytedious and time consuming process, involving several hours ofadditional labor.

In addition, speed is of the utmost importance in tensioning cables.Typically, a tensioner operator may do nothing but tension cables. Theoperator may be paid per pull, i.e. per cable tensioned, so the operatorwants to tension each cable as quickly as possible. For long cables, thetensioning device may stroke several times for each cable. Thus, thespeed of operation of the tensioning device is important.

The extension speed of the tensioner is determined by the flowrate ofhydraulic fluid to the tensioner, which is to a certain extent at leastunder the control of the operator. However, for single acting cylindersthe retraction speed of the tensioner is determined by the cylinders andparticularly by the springs inside the cylinders which act to returnthem. In addition, since a tensioner of this type is constantly beinghandled by the operator, it is important that the tensioner be easy touse, handle, move and supply hydraulic fluid to. Since these tensionersare also used on construction sites, they must also be rugged.

SUMMARY OF THE INVENTION

The invention provides a concrete reinforcement cable tensioner whichaddresses the above described needs. Thus, as in prior art concretereinforcement cable tensioners, a tensioner of the invention has one ormore hydraulic cylinders, a cable gripper mounted to the cylinders forgripping a cable and a seat for bearing directly or indirectly againstthe concrete, so that the gripper and the seat can be separated under ahydraulically generated force to apply tension to the reinforcementcable. However, a tensioner of the invention is improved, in one aspect,in that the gripper is mounted to each of the cylinders by a flangewhich engages a shoulder of each of the cylinders. Thus, the gripper canbe mounted in such a manner so that the length of cable required toprotrude from the green concrete slab is reduced, i.e., a shorter griplength is required, which can obviate the time consuming process ofhaving to extend a cable which does not extend beyond the slab farenough for the prior art tensioners to grip it. In this aspect, thegripper is mounted to the flange at a base end of the gripper, i.e., theend of the gripper which is closest to the base ends of the cylinders,which reduces the grip length by at least the thickness of the flange.

In another aspect, a tensioner of the invention is further provided witha spring external to cylinders for biasing the device to a retractedposition. Such a spring is in addition to the usual retraction springsinside the cylinders, and therefore helps speed up retraction of thedevice, which reduces the time needed for each cable pull.

In another aspect, the spring is contained in a handle of the tensioner.The handle is preferably a tube, in which the spring is contained, andthe spring is a compression spring which acts between a flange of anauxiliary spring rod and a cap of the tube. The rod extends through ahole in a cap of the tubular handle and is fixed at its distal end tothe piston rods of the cylinders, for example, through a yoke whichconnects the piston rods and to which is mounted the seat.

In another aspect, the device has multiple cylinders and the base endsof the cylinders are hydraulically connected by a manifold which iscommon to the cylinders. Multiple ports at various locations can beprovided in the manifold to permit a choice of places in which toestablish a hydraulic connection with the manifold to connect a pumpwith the device. Those ports of the manifold which are not used toconnect a pump to the cylinders are plugged.

These and other objects and advantages of the invention will be apparentfrom the detailed description and from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cable tensioner of the invention shownin a retracted position;

FIG. 2 is a perspective view of the tensioner of FIG. 1 shown in anextended position;

FIG. 3 is a top plan view of the tensioner of FIG. 1;

FIG. 4 is a front plan view of the tensioner of FIG. 1 and alsoillustrating a jaw retaining spring (the jaw retaining spring is alsoillustrated in FIGS. 5 and 6 but is not shown in FIGS. 1-3 for purposesof illustration);

FIG. 5 is a sectional view from the plane of the line 5—5 of FIG. 6;

FIG. 6 is a sectional view from the plane of the Line 6—6 of FIG. 5;

FIG. 7 is a front top perspective view of an assembly of a cable gripperand mounting flange of the tensioner of FIGS. 1-6; and

FIG. 8 is a top plan view of gripper jaws for the tensioner of FIGS. 1-6at a stage of manufacture prior to being cut apart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A concrete reinforcement cable tensioner 10 of the invention includes apair of single acting cylinders 12 and 14 which are bound together attheir base ends 24 by a manifold 16 and are bound together at a pointbetween their base ends 24 and rod ends 22 by a gripper mounting flange18. Each cylinder 12 and 14 is shouldered at the position where theflange 18 resides, indicated at 20, so that the outer diameter of eachcylinder 12 and 14 is greater between shoulder 20 and rod end 22 than itis between shoulder 20 and base end 24. The flange 18 has holes 19 in itsized to slide over the smaller diameter portions of the cylinders 12and 14 but not over the larger diameter portions, so that flange 18abuts shoulders 20 and is prevented thereby from moving any closer tothe rod ends 22. Set screws 26 in the flange 18 secure the flange 18against the shoulder 20.

The cylinders 12 and 14 are conventional (except for being stepped inoutside diameter as described above) single acting cylinders. The rod 30of each cylinder 12 and 14 is hollow (i.e. tubular) and an extensionspring 32 having one end fixed to the closed end 34 of the rod 30 andthe other end fixed to the base end 24 of the housing 36 of eachcylinder 12 and 14. The connections between the extension spring and therespective rod 30 and housing 36 are conventional, not shown in detail,and could be provided by any suitable means. For example, in one type ofconnection a connector is screwed into each end of the extension spring,and each connector is pinned to the respective rod 30 or housing 36.

The base ends 24 of the cylinders 12 and 14 are in hydraulic fluidcommunication with one another via manifold 16. Each cylinder 12 and 14has a single base end port 40 which is in fluid communication through anO-ring 42 with a port 44 formed in the manifold 16. The ports 44 are influid communication with one another by passageways formed within themanifold 16 including a pair of transverse passages 46 (FIG. 5), one foreach port 44, and a lateral passageway 48 which extends lengthwise allthe way through the manifold 16 and connects the passages 46.

The ends of the passageways 46 and 48 are tapped and are either pluggedwith a threaded plug or receive a threaded hydraulic connector, toprovide a total of four possible positions in which to supply hydraulicfluid to the device 10, two of which are at the ends of passageway 48and the other two of which are at the ends of the two passageways 46.

The manifold 16 is bolted to the base ends 24 of the cylinders 12 and 14by bolts 50 which extend through holes 52 in the manifold 16 that arethreaded into holes 54 in the base ends 24. A gripper 60 of generallyconventional design (except for the end at which it is anchored to thecylinders 12 and 14) includes a gripper housing 62 of the general shapeshown in FIG. 7 and wedge shaped gripper jaws 64 which slide on angledsurfaces within the gripper housing 62. Only the jaw 64 on the rightside of the gripper housing 62 is illustrated in full lines in FIG. 5and only the right jaw 64 is illustrated in FIG. 7 for purposes ofillustration. The jaw 64 on the left side in FIG. 5 is shown in phantom,it being understood that in operation both the left and right jaws wouldbe provided. Plates 73 are welded or otherwise affixed on the bottomside of housing 62 to help support the jaws 64 inside the housing 62.

The inside surfaces of the jaws 64 are serrated so as to grip a cable,as is well known. The serrated jaws 64 grip the cable and the tensiongenerated in the cable when the device 10 is extended tends to move thejaws 64 toward the end 65 (hereafter referred to as the rod end) of thehousing 62 which is closest to the rod ends 22 of the cylinders 12 and14, which because of the wedge shape and angled surfaces 71 inside thehousing 62 increases the strength of the grip exerted on the cable bythe jaws 64.

The jaws 64 are retained in the housing 62 and biased into the positionshown in FIG. 5, in which they are fully open, by a jaw retaining spring66 (FIGS. 4-6). The spring 66 is essentially a steel rod which is loopedand bent as indicated. The two legs 69 of the spring 66 extend throughslots 67 in the flange 18 and the end of each leg 69 is threaded intothe corresponding jaw 64. When the jaws 64 move together, the spring 66exerts a force on them which tends to return them to the home(disengaged) position shown in FIG. 5.

The serrations inside the jaws 64 can be made by forming a trapezoidallyshaped block 70 of the form shown in FIG. 8, which is equal to the twojaws 64 put together (plus the kerf along central axis 76 which iscreated when the two jaws 64 are cut apart). The block 70 is bored andtapped with the holes 72 into which the legs 69 of spring 66 arethreaded. The block 70 is also bored and tapped with a through bore 74,which is of a diameter approximately equal to the cable diameter. Theblock 70 is then cut apart along axis 76 to make the two jaws 64 (whichcut removes the material in the kerf). The serrations on the concaveinner sides 63 of the jaws 64 are provided by the screw threads of bore74, to grip the cable.

As best shown in FIG. 5, a cable channel 80 which opens downwardlyextends for the full length of the device 10 to permit engagement withthe cable and passage of the cable through the device 10. The gripperhousing 62 is bolted to the gripper mounting flange 18 by four bolts 82(only one shown in FIGS. 1 and 2), which extend through holes 85 in theflange 18 and are threaded into tapped holes 83 in the base end 87 ofthe housing 62 (which includes plates 73), which is the end of thehousing 62 closest to the base ends 24 of the cylinders 12 and 14.

The bolts 82 also secure a handle mounting flange 84 to the grippermounting flange 18. The handle mounting flange 84 is welded to a tubularhandle 86 which extends longitudinally with respect to the tensioner 10,parallel to the central axis of the tensioner 10 and above the cylinders12 and 14. The handle 86 is closed at its base end by a cap 88, whichmay be vented to permit air to enter the handle 86, and is closed at itsrod end by a cap 90 having a central hole through which an auxiliaryspring rod 92 extends for sliding movement relative to the cap 90.

The spring rod 92 is biased into the retracted position by a compressionspring 94. A flange or plunger 96 is fixed at the base end of the rod 92for the base end of the spring 94 to bear against and the rod end of thespring bears against the cap 90. The rod end of the rod 92 is secured bya screw 98 to a flange 100 which is bolted by bolts 102 to a yoke 104that is bolted to both rods 30 via bolt holes 91 (FIG. 5).Alternatively, the rod end of the rod 92 could extend through the flange100 and be threaded so as to be secured by a nut to the flange 100.Thus, as the device 10 is extended, the spring 94 becomes compressed soas to bias the rod 92 into the retracted position.

The bolts 102 also secure a plunger manifold 106 to the yoke 104. A seat108 is bolted on the opposite side of the yoke 104 from the manifold106. As shown in FIG. 5, a plunger 110 is reciprocable in the seat 108and is biased in an extended position by a pair of springs 112 which arecontained in bores 114 in the plunger manifold 106. The springs 112 arecompression springs which act between the plunger manifold 106 and aflange 116 of the plunger 110 so as to bias the plunger 110 in theextended position relative to the seat 108. The end of the plunger 110acts against the face of the grommet which holds the cable under tensionin the concrete slab. When the cable is pulled through the grommet bythe device 10, the grommet acts against the end face of the plunger 110to move it into a retracted position in which the grommet permits thecable to slide relative to it so that the cable can be tensioned.However, the plunger 10 maintains a biasing force on the grommet tendingto move the grommet into the engaged position in which it bites into thecable and holds the cable under tension.

As an alternative, the springs 112 can be replaced with hydraulicplungers or pistons and hydraulic pressure applied to the back side ofthe plungers via ports 120 in the plunger manifold 106 so as topositively seat the grommet so that the engagement of the grommet withthe cable is made fast after a tensioning operation.

We claim:
 1. In a concrete reinforcement cable tensioner of the typehaving one or more hydraulic cylinders, a cable gripper connected tosaid cylinder(s) for gripping a reinforcement cable and a seat forbearing directly or indirectly against a concrete slab so that thegripper and the seat can be moved apart under a hydraulically generatedforce to apply tension to the reinforcement cable, the improvementwherein said gripper is mounted to each said cylinder by a flange whichengages a shoulder of each said cylinder; and further comprising aspring external to said cylinder(s) for biasing said cylinder(s) to aretracted position.
 2. The improvement of claim 1, wherein said gripperis mounted to said flange at a base end of said gripper, said base endof said gripper being an end of said gripper which is distal from saidconcrete slab.
 3. The improvement of claim 1, wherein said spring iscontained in a handle of said tensioner.
 4. The improvement of claim 3,wherein said handle is a tube in which said spring is contained and saidspring is a compression spring which acts between a flange of anauxiliary spring rod and a cap of said tube.
 5. The improvement of claim4, wherein said rod extends through a hole in a cap of said tube and isfixed at its distal end to the piston rods of said cylinder(s).
 6. Theimprovement of claim 1, wherein said tensioner has multiple cylindersand base ends of said cylinders are hydraulically connected by amanifold which is common to said cylinders.
 7. In a concretereinforcement cable tensioner of the type having one or more hydrauliccylinders, a cable gripper connected to said cylinder(s) for gripping areinforcement cable and a seat for bearing directly or indirectlyagainst a concrete slab so that the gripper and the seat can be movedapart under a hydraulically generated force to apply tension to thereinforcement cable, the improvement wherein said tensioner furtherincludes a spring external to said cylinder(s) for biasing saidcylinder(s) to a retracted position, wherein said spring is contained ina handle of said tensioner.
 8. The improvement of claim 7, wherein saidhandle is a tube in which said spring is contained and said spring is acompression spring which acts between a flange of an auxiliary springrod and a cap of said tube.
 9. The improvement of claim 8, wherein saidrod extends through a hole in a cap of said tube and is fixed at itsdistal end to the piston rods of said cylinder(s).